1. Field of the Invention
The field of the invention relates to a process for the selective determination of the concentration of a substance (A) dissolved in a solvent by means of an osmotic cell having a rigid wall with a pressure measurement apparatus for the measurement of the hydrostatic pressure in the osmotic cell, and with a membrane which is permeable for the substance, by means of which the osmometer solution in the osmotic cell is brought into contact with the solution, the concentration of the substance in which is to be determined. First, using a reference solution brought into contact with the osmometer solution by means of the membrane, a working pressure P.sub.0 is established whereupon, after the replacement of the reference solution with the solution to be tested, the concentration of the permeable substance (A) in the solution to be tested is determined from the pressure curve which is established in the osmotic cell. The field of the invention also relates to apparatus for the performance of the process.
2. Description of the Prior Art
U.S. Pat. No. 4,706,495 entitled "Method and Apparatus for the Determination of Substances Dissolved in a Solvent", which corresponds to German Laid Open Patent Appln. No. 35 25 668, describes processes using an osmotic cell of the type described above, according to which the concentration of substances in a solution to be tested is determined from the pressure curve established in the osmotic cell. These patent publications, supra, are incorporated herein by reference as if the entire contents thereof were set forth herein.
The osmotic cell used has a rigid wall and also a rigid membrane, so that during the process, the change in the volume of the osmotic cell is very small.
The processes of the prior art of course make it possible to determine the concentration of a substance in a solution, if there are two or more substances in the solution. For this purpose, however, it is necessary to evaluate a large portion of the pressure curve established after the exchange of the solutions, up to the final pressure, or to use two osmotic cells with different membranes.